Plasma chemical vapor deposition (PCVD) is a main process for optical fiber preform rod processing, and a plasma microwave resonant cavity is a core part of a PCVD processing apparatus. The plasma microwave resonant cavity mainly includes a resonant cavity housing and a waveguide device connected to the resonant cavity housing. Coaxial through-holes are opened on two ends of the resonant cavity housing along an axial direction of the resonant cavity, a glass inner liner is disposed via the through-holes at the two ends and penetrates the resonant cavity and the through-holes at the two ends, and glass stop rings are disposed at two ends of the glass inner liner and used for axial positioning of the glass inner liner. In the prior art, the glass stop ring at one end of the glass inner liner is integrally formed with a glass cylinder of the glass inner liner in manufacturing, and the glass stop ring at the other end of the glass inner liner needs to be manufactured in a manner that the glass stop ring is mounted at an end of the glass cylinder after the glass inner liner is mounted to the resonant cavity housing and then the end of the glass cylinder is melted through hydrogen and oxygen combustion and turned inside out to press against the glass stop ring.
The structure of the glass inner liner has the following problems: (1). the field installation is complex and of high operation difficulty, and since the quartz glass needs to be melted at a temperature above 2000° C., in this high-temperature environment, the metal at the end of the resonant cavity may easily diffuse to the quartz glass inner liner and further diffuse to a deposition tube in the PCVD deposition process, so that the attenuation of the optical fiber preform increases and affects the processing quality of the optical fiber preform; (2). the glass which is melted and then turned inside out has certain stress after cool down, so that glass cracking and breakage may easily occur in use, and in a more serious case, product rejection and even damages to the apparatus may be caused; (3). if the mounted glass ring gets loose in use, fastening is required; however, the effect of secondary fastening of glass is undesirable and can hardly reach the requirement, which may affect the processing performance of the apparatus as well as the stability of the product quality; and (4). since the quartz glass inner liner and the glass stop ring are adhered at a high temperature, destructive detachment needs to be performed on the quartz glass inner liner and the stop ring when the resonant cavity is maintained or checked, and in this case, a new glass inner liner needs to be replaced and the cracked glass fragment may easily fall into the resonant cavity to cause damages to the resonant cavity.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.